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2 Installing the Instrument
Remote Sense Connections
SHOCK HAZARD, LETHAL VOLTAGES - Many models generate output voltages up to
2,000 VDC! Ensure that all instrument connections, load wiring, load and sense
connections are insulated using high-voltage wire. Always attach the safety cover
provided, so that no accidental contact with lethal voltages can occur.
Remote sensing improves the voltage regulation at the load by regulating the voltage there instead of
at the output terminals. This lets the power supply automatically compensate for the voltage drop in
the load leads. Remote sensing is especially useful for CV operation with load impedances that vary or
have significant load lead resistance. In current priority mode, the voltage limit settings are monitored
at the sense connections. Over-voltage protection is also monitored at the sense connections.
Connect the unit for remote sensing by first removing the local sense cable between the sense and
load terminals. Then make your sense and load connections as shown in the following figure. Note that
the two center terminals of the sense connector are not used.
Sense connectors accept wire sizes between AWG 16 (1.5 mm 2 ) maximum and AWG 24 (0.2 mm 2 )
minimum. Strip the wire insulation back 10 mm. Tighten the screws securely.
Connect the sense leads as close to the load as possible. Keep the sense wire-pair as short as possible
and twist or bundle it to reduce noise pickup. Do NOT bundle the sense wire-pair together with the
load leads; keep the load wires and sense wires separate. Sense wires are normally of a lighter gauge
than the load wiring.
Note that any voltage drop due to wire resistance in the sense leads can degrade the output voltage
regulation. As the voltage drop in the load leads increases, the load voltage regulation error due to
sense-lead resistance increases according to the following formula:
ΔV
= 2(V
(R
regulation
load
sense
R
is the resistance in ohms of each sense lead.
sense
V
is the voltage drop in each load lead.
load
S
is the internal sense protect resistor (see following table).
protect
The formula assumes that the voltage drop in the +/- load leads are equal.
76
/S
))
protect
Keysight RP7970 & RP7980 Series Operating and Service Guide
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